// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/files/memory_mapped_file.h"

#include <stddef.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

#include "base/logging.h"
#include "base/threading/thread_restrictions.h"
#include "build/build_config.h"

namespace base {

MemoryMappedFile::MemoryMappedFile()
    : data_(NULL)
    , length_(0)
{
}

#if !defined(OS_NACL)
bool MemoryMappedFile::MapFileRegionToMemory(
    const MemoryMappedFile::Region& region,
    Access access)
{
    ThreadRestrictions::AssertIOAllowed();

    off_t map_start = 0;
    size_t map_size = 0;
    int32_t data_offset = 0;

    if (region == MemoryMappedFile::Region::kWholeFile) {
        int64_t file_len = file_.GetLength();
        if (file_len == -1) {
            DPLOG(ERROR) << "fstat " << file_.GetPlatformFile();
            return false;
        }
        map_size = static_cast<size_t>(file_len);
        length_ = map_size;
    } else {
        // The region can be arbitrarily aligned. mmap, instead, requires both the
        // start and size to be page-aligned. Hence, we map here the page-aligned
        // outer region [|aligned_start|, |aligned_start| + |size|] which contains
        // |region| and then add up the |data_offset| displacement.
        int64_t aligned_start = 0;
        int64_t aligned_size = 0;
        CalculateVMAlignedBoundaries(region.offset,
            region.size,
            &aligned_start,
            &aligned_size,
            &data_offset);

        // Ensure that the casts in the mmap call below are sane.
        if (aligned_start < 0 || aligned_size < 0 || aligned_start > std::numeric_limits<off_t>::max() || static_cast<uint64_t>(aligned_size) > std::numeric_limits<size_t>::max() || static_cast<uint64_t>(region.size) > std::numeric_limits<size_t>::max()) {
            DLOG(ERROR) << "Region bounds are not valid for mmap";
            return false;
        }

        map_start = static_cast<off_t>(aligned_start);
        map_size = static_cast<size_t>(aligned_size);
        length_ = static_cast<size_t>(region.size);
    }

    int flags = 0;
    switch (access) {
    case READ_ONLY:
        flags |= PROT_READ;
        break;
    case READ_WRITE:
        flags |= PROT_READ | PROT_WRITE;
        break;
    case READ_WRITE_EXTEND:
        // POSIX won't auto-extend the file when it is written so it must first
        // be explicitly extended to the maximum size. Zeros will fill the new
        // space.
        file_.SetLength(std::max(file_.GetLength(), region.offset + region.size));
        flags |= PROT_READ | PROT_WRITE;
        break;
    }
    data_ = static_cast<uint8_t*>(mmap(NULL, map_size, flags, MAP_SHARED,
        file_.GetPlatformFile(), map_start));
    if (data_ == MAP_FAILED) {
        DPLOG(ERROR) << "mmap " << file_.GetPlatformFile();
        return false;
    }

    data_ += data_offset;
    return true;
}
#endif

void MemoryMappedFile::CloseHandles()
{
    ThreadRestrictions::AssertIOAllowed();

    if (data_ != NULL)
        munmap(data_, length_);
    file_.Close();

    data_ = NULL;
    length_ = 0;
}

} // namespace base
